The problem lies where you are using the divisions for the second anchors in your list. The only purpose of these divisions I see is for font sizing, so I think you should move this sizing to css and remove the divs.

It's the usual case if IE making up its own rules, instead of following the standard.

IE renders a block object of a defined size by putting the margin, border, and padding INSIDE the defined size.

FF renders a block object of a defined size by putting the margin, border, and padding OUTSIDE the defined size.

The only way to get both to work the same is to nest divs, one with the defined size, and the other with the margin, border, and padding you want. Nest them with the margin, border, and padding div on the side (inside or outside) of the defined size div that you want it on.